: Candidate: The Candidate had subspecialty training in Mexico and previous research experience in the USA in the field of gene regulation by pro-inflammatory cytokines. Recently, he has concluded his fellowship training in rheumatology and has been appointed as Lecturer in the Division of Rheumatology. This project represents an expansion of the Candidate's research interests in the field of inflammation. This experience will add significant training in the area of mouse models and protein processing. If funded, the award will be instrumental in the Candidate's transition to independence as a clinician scientist, and his further academic progress toward professorship status. The mentor: Dr. Deborah Gumucio, has extensive experience in mouse models of human disease and in transcriptional regulation of gene expression. The mentor's fully equipped molecular biology laboratory, and core facilities (vector, sequencing, animal) in the Department of Cell and Developmental Biology at the University of Michigan will be available to the Candidate. Research Project: Mutations of pyrin cause familial Mediterranean fever (FMF), a disease characterized by spontaneous episodes of arthritis or serosal inflammation. Although pyrin is predicted to play a role in the inflammatory response, its function is still unknown. Pyrin is known to be expressed in neutrophils, macrophages, eosinophils and peritoneal and dermal fibroblasts. Evidence is presented here that pyrin is subject to alternative splicing and that the profile of splice isoforms is different in synovial cells than it is in neutrophils and macrophages. Exposure of synovial cells to inflammatory cytokines results in induction of specific splice isoforms. Interestingly, while full-length pyrin is cytosolic, some of the splice isoforms are localized to the nucleus. The further understanding of the profile of these isoforms in synovial cells, and an analysis of their functional properties is goal of this proposal. New data are presented that indicate that nuclear pyrin isoforms might interact with a post-transcriptional repressor, called hLARK. The possibility that this interaction might affect the production of cytokines by synovial cells will be tested. Other pyrin-interacting proteins are members of the apoptosis pathway, and modeling studies indicate that pyrin's exon 1 forms a death domain-related structure. The following central hypothesis underlies the work proposed: Pyrin may function to regulate apoptosis, inflammation and cytokine production in synovial cells. This function may require tight regulation of pyrin at several levels (transcription, splicing, translation). The following specific aims are designed to test this hypothesis: Aim 1: To examine the regulation of pyrin (transcription, splicing, translation, and cellular localization) in human synoviocytes under. basal and stimulated conditions. Also, to examine the possibility that pyrin, through its interaction with hLARK, modulates cytokine expression. Aim 2: To examine the levels of pyrin mRNA and protein in inflammatory cells from individuals with arthritis and other inflammatory conditions. Aim 3: To determine whether wild type pyrin modulates inflammation and/or apoptosis in experimental arthritis and peritonitis produced in mouse models (mice that over-express human pyrin; pyrin deficient mice; mice in which the endogenous pyrin locus has been modified to resemble human mutant pyrin). The work has the potential to lead to a greater understanding of the function of pyrin in inflammatory pathways in the joint. These findings may be relevant not only to the pathophysiology of FMF but also to inflammatory pathways in other syndromes of joint inflammation.